In intelligent buildings and FA factories, electronic appliances and communication devices such as personal computers, office-automation devices, factory-automation devices etc. have been generally introduced. As a result, erroneous operations of electronic devices, as well as electronic wave disturbance such as communication disturbance, which occur inside these buildings and factories due to the electromagnetic wave radiated from the electronic appliances and the communication devices as described above or undesirable electromagnetic wave coming from the outside of the environment, have now become a significant social problem.
In order to prevent such leakage of undesirable electromagnetic wave from the environment, as well as erroneous operations of electronic devices and electronic wave disturbance such as communication disturbance due to invasion of extrinsic electromagnetic wave, it has been considered that an information network using optical fibers, coaxial cables or the like is established inside an intelligent building or a FA factory so that information can be transmitted/received rapidly and accurately. However, there is a problem, in this method, that construction of such a network costs a lot of money. Therefore, there has been proposed another method in which the whole building is shielded from the outside environment and information exchange inside the building is carried out by wireless communication. In order to effect this method, it has conventionally been attempted that metal plates or metal foils of iron, copper, aluminum or the like as electromagnetic wave shielding materials are laminated to building materials such as board materials or a wall material which shields electromagnetic wave is employed.
Further, at opening/closing portions such as doors and windows, a gasket for shielding electromagnetic wave is generally provided, so that the undesirable electromagnetic wave radiated from outside of the environment, as well as the electromagnetic wave which leaks from inside of the environment, can be shielded.
Examples of such a gasket include a gasket produced by the steps of: slicing an elastic foam block such as polyurethane sponge by a predetermined thickness by a slicer; cutting each slice to pieces having a predetermined width, thereby to obtain short, strap-like structures each having a rectangular section; optionally connecting one structure with another at the ends thereof, thereby to obtain a long, strap-like structure; and laminating a conductive sheet around each strap-like structure by way of an adhesive agent layer, the conductive sheet being composed of an aluminum foil laminate film or a conductive woven cloth around which a film layer of copper, nickel or the like has been formed, and a gasket for shielding electromagnetic wave which is produced by providing a metal film on the strap-like structure itself.